LETTER or group of letters added at the end of a word to CHANGE its meaning or function.'Prevent' means to keep from happening or existing.Let us explore the options:The first option 'able' when added as a suffix to the word 'prevent', it becomes 'preventable' which means able to be prevented or avoided.The second option 'ing' when added as a suffix to the word 'prevent', it becomes 'preventing' which is a gerund or present participle of 'prevent'.The third option 'ive' when added as a suffix to the word 'prevent', it becomes 'preventive' which means devoted to or concerned with the PREVENTION: Precautionary.The fourth option 'ious' when added as a suffix to the word 'prevent', it becomes 'preventious' which do not have meaning or existence.Hence, the fourth option is not suitable as a suffix for the word 'prevent'. Extra- Bites- There are two types of suffixes: vowel and consonant.Vowel suffixes include endings such as "-ing, -able/ -ible, -ous, -ive, -ED, -ER,-es, -end".Consonant suffixes include endings such as "-s, -less, -ness, - ment, and -ly".